Recent developments in medicine have shown that the effects of respiratory aliments and post operative convalescence can be reduced through the continual administration of oxygen to a patient.
Most often the administration of oxygen to the patient is achieved through the use of some type of oxygen mask. Unfortunately, most oxygen masks are cumbersome and require a seal to be formed with the face of each patient. Without such a seal, a desired oxygen flow cannot be achieved.
The need of a face seal was elminated by the use of nasal cannulas such as disclosed in U.S. Pat. No. 3,915,173. In this device, a tube inserted in the nasal cavity has bulbular sections for sealing the oro-pharyngeal and the endotracheal areas from the atmosphere to directly supply the lungs with a breathable oxygen enriched fluid. As long as the patient is under the influence of anesthesia, this post operative cannula device is satisfactory. However, when the patient awakes, the tube causes an interference which hampers talking since exhalation gases are expelled through a constant flow valve in the supply conduit and not through the mouth. Thus, when the patient is revived, a standard cannula, such as disclosed in U.S. Pat. No. 3,802,431 is utilized to supply the needed oxygen enriched breathable fluid. With this cannula, the patient can eat and talk without discomfort. However, with all these cannulas, a constant flow of oxygen at the maximum usage rate is always necessary to assure proper respiratory medication.
Constant flow of the breathable fluid results in considerable loss of oxygen since a patient is normally inhaling only approximately 40% of the time while the remaining oxygen flow is lost to the atmosphere without helping the patient. In order to conserve oxygen, a control means as taught in U.S. Pat. No. 3,400,713, was devised. This control means has a belt which surrounds the waist of the patient and with each inhalation and exhalation, expansion and contraction of the lungs allows a resilient means to operate a valve which opens and shuts the communication of the supply port connected to the oxygen supply. Medical investigations have found the most beneficial use of oxygen occurs during the initial portion of the inhalation period. Unfortunately, the delay between the movement of the chest of the patient and the operation of the valve results in a corresponding delay in the communication of oxygen enriched breathable fluid into the lungs.